Increased demands on battery performance and economics of battery manufacture as well as recent advances in battery technology have provided new momentum to the development and production of bipolar lead acid batteries. However, despite various improved compositions and methods, various fundamental problems in the manufacture of substrates and current collectors remained. Moreover, despite various advances in bipolar battery design, relatively lame quantities of metallic lead are still required to retain structural stability during manufacture and repeated charge/discharge cycles.
For example, it is known in the art to weld together pure lead grids and pure lead plates to form a composite collector structure with relatively low internal impedance and at least somewhat increased oxidation and corrosion resistance as described in U.S. Pat. No. 3,806,696. This and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
However, where such batteries are subject to deep cycling, a PbSO4/PbOx layer is formed that will act as an insulator and so leads to premature capacity loss of the battery. Alternatively, various lead alloys (e.g., lead-calcium alloy) can be used together with a pure lead substrate as shown in U.S. Pat. No. 6,620,551 to so avoid formation of the insulating layer. Unfortunately, as the conductive grid is in most cases laminated to the lead substrate, delamination will ultimately reduce the lifetime of such batteries. Moreover, and regardless of the type of lead grid material, significant weight is added to the battery by virtue of having a conductive grid.
Similarly, where the substrate is a lead plate or a lead-coated plate, electrolyte creep from one cell to is often unavoidable and will internally short circuit the battery. In the same manner, difficulties with assembly of bipole elements into a bipolar battery stack remain. For example, it is known to stack and seal cells using certain sealants or sealing devices. While such approach tends to increase complexity in manufacture, it still often provides undesirable results, especially where the battery is run over numerous cycles. To overcome at least some of the problems associated with known sealants or sealing devices, bipoles may be pressed together to improve sealing of the gap. However, over-compression will negatively affect battery performance.
Therefore, even though numerous devices and methods of lead acid bipolar batteries are known in the art, all or almost all of them suffer from various disadvantages. Thus, there is still a need to provide improved lead acid bipolar batteries and production processes.